Field of the Invention
The present invention relates to audio signal processing and, more specifically but not exclusively, to beamforming for spherical eigenbeamforming microphone arrays.
Description of the Related Art
This section introduces aspects that may help facilitate a better understanding of the invention. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is prior art or what is not prior art.
Spherical microphone arrays have become a subject of interest in recent years [Refs. 1-4]. Compared to “conventional” arrays or single microphones, they provide the following advantages: steerable in 3-D space, arbitrary beampattern (within physical limits), independent control of beampattern and steering direction, easy beampattern design due to orthonormal “building blocks,” compact size, and low computational complexity. With these characteristics, it is appealing to a wide variety of applications such as music and film recording, wave-field synthesis recording, audio conferencing, surveillance, and architectural acoustics measurements.
U.S. Pat. Nos. 7,587,054 and 8,433,075 describe spherical microphone arrays that use a spherical harmonic decomposition of the acoustic sound field to decompose the sound field into a set of orthogonal eigenbeams [Refs. 3-4]. These eigenbeams are the orthonormal “building blocks” that are then combined in a weight-and-sum fashion to realize any general beamformer up to the maximum degree of the spherical harmonic (SH) decomposition.